The disclosed technology relates to a process for preparing a bridged alkaline earth metal alkylphenate such as dodecylphenate containing a reduced amount of monomeric alkylphenol.
Phenol-based detergents are known. Among these are phenates based on phenolic monomers, linked with sulfur bridges or alkylene bridges such as methylene linkages derived from formaldehyde. The phenolic monomers themselves are typically substituted with an aliphatic hydrocarbyl group to provide a measure of oil solubility. The hydrocarbyl groups may be alkyl groups: historically, dodecylphenol (or propylene tetramer-substituted phenol) has been widely used. An early reference to basic sulfurized polyvalent metal phenates is U.S. Pat. No. 2,680,096, Walker et al., Jun. 1, 1954.
Recently, however, certain alkylphenols and products prepared from them have come under increased scrutiny due to their association as potential endocrine disruptive materials. In particular, alkylphenol detergents which are based on oligomers of C12 alkyl phenols may contain residual monomeric C12 alkyl phenol species. There is interest, therefore, in developing alkyl-substituted phenate detergents, for uses in lubricants, fuels, and as industrial additives, which contain a reduced amount of monomeric dodecylphenol component.
There have been several efforts to prepare phenate detergents that do not contain C12 alkyl phenols or contain reduced amounts of such materials. In some cases these efforts have involved avoiding or minimizing the presence of C12 alkylphenol as a reactant. For instance, U.S. Pat. No. 7,435,709, Stonebraker et al., Oct. 14, 2008, discloses a linear alkylphenol-derived detergent substantially free of endocrine disruptive chemicals. It comprises a salt of a reaction product of (1) an olefin having at least 10 carbon atoms, where greater than 90 mole % of the olefin is a linear C20-C30 n-alpha olefin, and wherein less than 10 mole % of the olefin is a linear olefin of less than 20 carbon atoms, and less than 5 mole % of the olefin a branched chain olefin of 18 carbons or less, and (2) a hydroxyaromatic compound.
U.S. Pat. No. 3,464,970, Sakai et al., Sep. 2, 1969, discloses a process for preparing overbased sulfurized calcium phenates. In an example, an alkylphenol mixture was reacted with calcium oxide and elemental sulfur. In the alkylphenol mixture, those having C4 radicals were 6 mole percent, those having C8 radicals were 18 mole percent, and those having C12 radicals were 76 mole percent. Of the alkylphenols having C8 alkyl radicals, about 36 mole percent was mono-octyl phenol and about 64 percent was di-octylphenol.
U.S. Pat. No. 6,610,637, Curtis et al., Aug. 26, 2003, discloses sulfur-free functionalized alkyl phenol detergents. The functionalization may be an additional hydrocarbyl group such as (among others listed) t-butyl groups.
U.S. Pat. No. 5,840,672, Gatto, Nov. 24, 1998, discloses sulfurized hindered phenols as antioxidants.
U.S. Pat. No. 6,310,009, Carrick et al., Oct. 30, 2001, discloses a saligenin derivative such as the magnesium salt represented by the formula
an additive for a lubricating composition. Preferably X is —CHO or —CH2OH, and Y is —CH2— or —CH2OCH2—. R is a hydrocarbyl group containing 1 to 60 carbon atoms and m is 0 to 10.
U.S. Pat. No. 3,992,308, Malec et al., Nov. 16, 1976, discloses a lubricating oil composition containing a sulfurized reaction product of mixed tertiary alkyl phenols with formaldehyde. When used in lubricating oil, they impart improved wear and corrosion inhibiting properties in addition to being effective antioxidants. In an example, 75 weight percent of 2,5-di-tert-butylphenol, 15 weight percent ortho-tertiary butylphenol, and 10 weight percent of 2,4,6-tri-tert-butylphenol was reacted with paraformaldehyde.
U.S. Pat. No. 4,221,673, Robson et al., Sep. 9, 1980, discloses overbased metal phenates prepared by reacting a basic metallic compound with a mixture of an alkyl phenol and an alkydihdroxybenzene. The phenolic composition may comprise certain sulphurised alkyl phenols. An R group substituent is a hydrocarbyl or substituted hydrocarbyl group containing up to 60 carbon atoms. In examples, compositions are prepared from dodecyl phenol and nonyl catechol.
The disclosed technology provides a method for preparing phenate detergent which contains a reduced amount of monomeric dodecylphenol within an oligomeric dodecylphenol composition or, more generally, a reduced amount of monomeric alkylphenol in an oligomeric alkylphenol composition. In certain embodiments such detergents will also exhibit improved antioxidant properties.